Two entities are the major players for stormwater projects—green and gray—in Madison. One of those players is the city itself, which as of 2014 had a population more than 245,000. The other is the University of Wisconsin’s (UW’s) main branch. Its flagship campus of the UW system covers 936 acres in Madison.
“We have four miles of lakefront on Lake Mendota. We’re always trying to manage stormwater from the lake quality standpoint,” says Gary Brown, FASLA, UW’s landscape architect and director of Facilities Planning and Management. “Now we’re working on both stormwater quality and quantity.”
He adds, “We’re the largest landowner. We’re trying to do cutting-edge research, so people look to us for new solutions. We’re also state funded, and the state likes to spend money on tried and true methods.”
Part of the challenge of managing stormwater on the urban UW campus is the university’s location. “We’re on an isthmus between two major lakes and between two different watersheds,” explains Brown.
He says researchers in various UW departments are working on stormwater issues. “The engineering faculty is looking at temporary controls and leak protection. The landscape architects are doing research on plants—prairie species that are very deeply rooted.”
Like many large universities, UW has the large buildings—dormitories, parking garages, athletic facilities, office buildings, student activities buildings—that make green roofs economically feasible for managing stormwater over large impervious sites.
“Green roofs are not just about stormwater. They help with temperature control, provide an ecosystem and habitat, and reduce the urban heat island effect,” notes Brown.
But he laments, “The local municipalities don’t count green roofs toward stormwater mitigation because they’re frozen for six months a year until the early spring rains. But the growing media doesn’t freeze solid. It still holds some water.”
The Education Building at UW-Madison is impressive for its different types of green roofs. On the third floor is an extensive green roof with a patio area, off of the dean’s suite of offices. Brown says that with its beautiful view of Lake Mendota in the distance, the roof is a perfect site for the dean to recruit new faculty members.
“On the second floor there is a mix of intensive and extensive green roofs. The roof blends on the hillside and covers a parking lot below. It goes out to a meadow landscape. Trees, including small hawthorn and drab apples, are planted in boxes,” says Brown.
Another green roof at UW, with the extensive tray system, is atop University Square. One third of this public-private project is owned by UW. It covers a full block, with private retail businesses, private apartments, and offices for student health and other student services.
The green roofs above the Education Building, Union Square, and the Gordon Dining and Event Center were designed by the landscape architecture firm of Smith Group JJR.
UW has a well-developed plan for managing its stormwater. That plan includes some innovative projects with green infrastructure. Besides the green roofs, bioswales are adjacent to a number of parking lots, dormitories, and other large buildings.
The larger bioswales at the Dejope residential complex are located near the street. They handle runoff from the street and from the building. This project was designed by the landscape architecture firm of Ken Saiki Design.
Green roof on the Education Building right after installation
Brown says porous asphalt was originally applied at parking lot 34, but “it degraded. The mix wasn’t right, and we had problems. The bioswale worked a lot better on this lot, which is adjacent to the lake. We had to replace the porous asphalt with standard asphalt.”
He notes, “Porous concrete works better for us. The contractors are starting to figure out the right mix. On the south side of buildings we don’t have to use salt or sand. The porous concrete has a texture to it, and if we can get the snow cleared off before walkers pack it down, it’s fine.”
Snow is removed from campus walks and driveways and transported to a back area of the campus next to a manmade marsh. Brown says the snow pile lasts until June.
“The migratory birds love it, with the little puddles of melting snow. We’re monitoring the chlorine in the runoff. The local and WDNR [Wisconsin Department of Natural Resources] folks said it’s fine, that the [surrounding] berms are holding the water [until it evaporates],” he adds.
“We have a few rain barrels on campus, in one of our garden areas. They’re used by the horticulture department,” says Brown.
The UW arboretum has its own stormwater issues. The 1,200-acre site is at the lowest point within the Lake Wingra watershed, so it receives hundreds of millions of runoff annually. The arboretum is surrounded by marshland. Slowing down the flow of stormwater through its acreage and infiltrating as much as possible is essential to protect the lake.
The arboretum’s Secret Pond was “originally a natural channel that flowed into Lake Wingra,” says Brown. Sometime in the 1980s a larger channel was created to help the stormwater flow better. Eventually the increasing amount of impervious surface within the watershed led to plants dying and lower water quality in the downstream lake.
Rebuilding Secret Pond and expanding it to 1.4 acres was the solution. A clay lining was included to trap and filter out pollutants.
A naturalized, 350-foot meandering channel was created with a larger forebay up near the street to allow much of the sediment to drop out there. The channel and a stilling pool slow the velocity of the runoff and help stop erosion of the banks. Native wetland plants were installed.
The new version of Secret Pond helps keep sand and heavy metals out of the lake. The total suspended solids (TSS) entering into the lake were reduced by 52%.
The update at Secret Pond was another joint university and city project. It was designed by John Lindert, ASLA, of Strand Associates.
Also part of the arboretum, Marion Dunn Pond, through a joint effort with the city of Madison, was cleaned out and new embankments were added. Brown says that the concern here was controlling phosphorus. Alum (aluminum sulfate) was applied, because it binds with phosphorus. Research is still ongoing to see how well the alum reduces phosphorus levels in the lake.
Adams Street rain garden in June 2006, about a week after planting
Another project to protect the lakes is run by the city of Madison. This program was developed to encourage the installation of residential rain gardens. Greg Fries, principal engineer for the city, says, “It’s a good program. We started in 2005 and have installed 585 rain gardens. That’s more than halfway to our goal of 1,000.”
That number includes both regular rain gardens and those located within a residential right of way, or terrace, beside the sidewalk. “The terrace rain gardens are the ones we do when a street is being reconstructed or resurfaced,” explains Fries.
There are several factors that limit where a terrace rain garden can be installed. That means that not every homeowner who wants a rain garden has a site that qualifies for its installation. The site can’t be on an avenue or bus route, because these are salted during winter. That road salt would damage many of the plants in the rain gardens.
The terrace rain gardens are located primarily on side streets. Sand is the only traction material used on these less-traveled streets.
The terraces must be at least 10 feet wide. They must be large enough so that the rain garden can be at least 15 feet long. In addition, terraces cannot be too steep in any direction. If very high groundwater is present, a rain garden cannot be installed.
Trees can also pose problems with the plants in rain gardens. The city requires that any trees must be at least 10 feet from the edge of the rain garden.
“We charge the property owner $100 to install the rain garden, and they are required to maintain the garden. It costs the city about $2,500. We put in one plant per square foot. At $3 per plant in a terrace rain garden, a 10-foot by 20-foot space costs $600 just for the plants,” explains Fries.
“The homeowner can pick from examples of gardens that are on our website. There are a lot of choices. In 2005, when the program started, we let each property owner meet with a landscaper to choose plants, and that got out of hand. It was taking too much time,” says Fries.
Bioswale at the Dejope Residence Hall just after planting
Now the standard choices of plant palettes (clearly labeled for full sun, full shade, or partial shade sites and formal or casual style) seem to please everyone, and installation goes faster. Fries says that if a homeowner doesn’t like a particular plant, the city is willing to substitute for it.
One attractive standard garden focuses on plants with blue flowers and includes sky blue aster, wild geranium, great blue lobelia, and brown fox sedge. A rain garden created to attract butterflies features such plants as black-eyed susan, marsh phlox, prairie dropseed, columbine, and butterfly weed.
“Purple coneflower is the most popular native plant. It’s pretty and it spreads well,” he notes. “We put in a mix of plants, and the plants that are really suited for that garden will spread. We rarely have to replant.”
The terrace rain gardens along Adams Street were among the first ones the city of Madison installed. Now, more than 10 years later, these gardens are thriving and working well.
Fries says the city has constructed about 20 rain gardens on public land. These rain gardens are generally designed to handle runoff from parking lots at public parks and facilities.
Bioswale at the Dejope Residence Hall two years after planting
Rain gardens have become popular in Madison and surrounding areas because of state legislation requiring green infrastructure. “NR 151 of the state code, which was adopted in 2004, has really driven the installation of rain gardens and bioretention areas on all private redevelopment sites and almost any parking areas,” says Fries. “There are well over 200 on private land around the city.”
He notes that in the 10 years since the rain garden program began, public knowledge of rain gardens has increased tremendously. “At a public meeting, if I ask who knows what a rain garden is, 90% of the people there will raise their hands.”
He adds, “Bioretention areas and bioswales are driven by the way regulations were written in 2004 and updated in 2011. Those regulations really drove change from traditional retention ponds as part of any private project.”
Fries admits he was skeptical of rain gardens at first. The city installed one on a water utility building site in a highly urban area as a test. Monitoring by the US Geological Survey with double-ring infiltration showed that a control site of just grass infiltrated one-tenth of an inch of runoff per hour. The side with native plants infiltrated 1.5 inches of runoff per hour.
“We did this in winter, and even after a big snow melt there was no standing water. The grass side had standing water,” recalls Fries.
Fries says that nine rain gardens [of the typical size used there] have the same TSS removal rate as three large catch basins. “Rain gardens do their job in a very public way. There are some benefits to that, which is true of public works in general.”
Several municipal building in Madison have green roofs. They include Fire Station No. 12, which earned Platinum LEED certification and was designed by Strand Associates, and the addition at the Engineering Services Building, designed by the landscape architecture firm of Ken Saiki Design.
Green roof on the Cooper Hall School of Nursing
The city of Madison gives stormwater credit for intensive green roofs. Extensive green roofs, with only a few inches of soil, do not earn stormwater credit.
“They are basically considered the same as pervious areas,” says Fries. “The 8- to 12-or-more-inches-deep soil system drives the cost of these roofs up, though.”
Fries says that Madison’s challenges in managing its stormwater are “just geography. We are built between two lakes. We’re built on silt. The water table is so high that infiltration is difficult.”
In the city’s green streets approach, “there are a number of techniques that we are piloting and actively using in different stages of development as we try to infiltrate more stormwater,” says Chris Petykowski, also a Principal Engineer with the city of Madison.
Madison’s soil has “some sand seams. A lot of it is clay. We’re trying the techniques wherever opportunity exists, citywide and in residential areas,” explains Petykowski.
Madison doesn’t have an officially funded green streets program, so the city’s approach to trying new methods to manage stormwater through the use of green infrastructure is very informal. Rather than an entire street being done, different BMPs have been, and will be, installed and monitored in varied locations.
“Rain gardens are used the most,” says Petykowski. “We’ve been experimenting with permeable pavement, too.” The permeable pavement has worked fine during winter, but it was installed in an area where there is very little traffic. That’s because no homes have yet been built on that particular street.
Madison is also trying tree vaults. “We support the sidewalk so the tree roots don’t have any pressure on them, so they can grow well,” explains Petykowski.
When asked about the challenges of managing stormwater in Madison, Petykowski says that salt used on
the streets during the long Wisconsin winters is one “when we’re trying to pick out the best place for a stormwater pond or trying to infiltrate stormwater.”
Madison has reduced its use of road salt. Workers are trained to use the least amount of salt that will produce the desired result. Only major roads and those streets that are on bus routes, or about 45% of the streets in the city, are salted. All of the other streets in Madison are treated with sand alone. Compared to other cities of similar size and climate, Madison is using much less road salt.
The Willow Creek project is an interesting joint effort of the city of Madison, Dane County, WDNR, and UW-Madison. The watershed of several square miles drains to a small creek that runs through the urban campus.
“It’s a backwater of Lake Mendota, a finger of the lake—shallow standing water, not flowing most of the time,” says Fries.
From Willow Creek, runoff flows into Lake Mendota. The surrounding area was all built up by 1968. No stormwater measures had been installed.
“The creek has been the recipient of unrestricted stormwater. Madison uses a lot of sand [for traction on roads in winter], so sediment was deposited in the creek over the years,” explains Fries.
The project will include a concrete bottom catch basin to catch sediment. A large weir at the downstream, or outlet, end will slow the flow of the creek.
“We’re installing a large forebay, a 200-foot-long drop structure,” says Brown.
“Above the water level it will look natural. We can lower the water level and drive a skid loader down to clean out the sediment,” says Fries.
“This will have a system we can maintain to trap sediment at the headwaters. We’ll restore the remainder of the channel,” adds Fries.
Construction on the Willow Creek project will start in July and will be finished in the fall. The city is leading the first phase of the construction, even though the project is on UW land. The university will lead the second part, which involves restoring the creek and dredging the lake. This dredging will cover 1,000 feet and create an island in Lake Mendota.
Brown says the increased water depth from the dredging should please boaters, fishermen, and UW’s crew team, whose members “had to adjust their route because the water is so shallow.”
Managing stormwater in Madison and throughout the state of Wisconsin has been Roger Bannerman’s work for years. Now working with the US Geological Survey, he has served on numerous committees that develop and review standards for various types of stormwater BMPs and aspects of stormwater management.
“One of the challenges is regional rain patterns. The intense storms we get are very different from, say, the drizzle in Seattle,” says Bannerman.
“People have to basically follow the criteria [for their type of stormwater BMP]. Then their project is approved. The committee loves it because it simplifies the design process, including that of green infrastructure,” he explains.
The various stormwater standards committees in Wisconsin revise standards they set earlier as new research becomes available. The committees include people from various municipal and state agencies, universities, private firms, and industry.
“There is more buy-in when they are all part of the process,” explains Bannerman. “We’ve had some good discussions, and we have a very transparent approach.”
Bannerman is particularly interested in monitoring stormwater BMPs, both the process and the instrumentation. He disapproves of results that rely on what happened during only a few storms.
“We like to have [results from] at least 20 storms,” he says.
He is impressed with a new, more sophisticated stormwater monitor. The Depth Integrated Sampler Arm (DISA) “is more expensive [than commonly used monitors], but it’s cheaper in the long run because it provides much better data.”
What makes the patented DISA monitor so effective is stratification. Rather than the usual intake from the bottom of a pipe, the sampler’s arm moves up and down. It changes as the depth of the water changes, thus delivering an integrated sample from top, middle, and bottom water levels.
“Most stormwater control measures are driven by particle distribution,” says Bannerman. “Engineers really pay attention to regulations. The new DISA concept is coming into play, and ignoring that could cost them a lot.”
He says, “We’re supportive of green infrastructure. Our performance standards require volume control in new developments. The model can do green infrastructure [as well as gray].”
Factors that influence the adoption of green infrastructure include the initial cost and maintenance costs and responsibility. “That’s always the first question about rain gardens—who will maintain them,” notes Bannerman.
He adds, “One of the drivers is that we have volume control requirements if you build something new. People have realized that green infrastructure can meet their TMDL [total maximum daily load] requirements.”
Looking ahead, Bannerman says, “I’m hopeful. People are showing more interest in green infrastructure and prevention. Proprietary devices will play a role [in its adoption.]”
